1. Field of the Invention
This invention relates generally to the field of construction utilizing solder as an attachment means, and in particular, to a method for soldering conventionally unsolderable surfaces to other conventionally unsolderable surfaces or conventionally solderable surfaces.
2. Prior Art
The problem of soldering conventionally unsolderable surfaces has also been characterized as the difficulty of creating a tinnable surface, that is, a surface to which solder will adhere. Various approaches to this problem are demonstrated in three areas: the formation of circuit boards, the splicing of fiber optical rods and decorative stained glass construction.
With regard to printed circuit boards, a method is known which comprises printing a curable adhesive ink in a predetermined pattern on an insulating base, applying a metal powder onto the printed insulating base whereby discrete particles of the metal powder are retained on the printed adhesive ink only, and curing the adhesive ink so as to fix the discrete particles of metal powder thereon. The remaining steps involve immersing the insulating base in an aqueous solution of stannous chloride and palladium chloride for producing an activating agent thereon, and subsequently treating the base with an electroless metal deposition bath. In another method, a printed circuit board is constructed by applying an adhesive to the surface of an organic resin plate in an electrical circuit pattern, scattering metal powders on the adhesive, pressing the scattered metal powders, so that the metal powders are partly imbedded in and partly exposed to the surface of the adhesive, curing the adhesive combined with the metal powders and depositing a conductive metal coating on the exposed metal powders by electroless plating whereby the exposed metal powders act as a catalyzer. Both of these methods require the step of electroless plating prior to soldering, whereas the subject invention requires no such step. Further, although it is noted that the resultant electrical circuit path is strong enough to stand up to soldering, there is no indication that such a bond would be strong enough to hold structural members together.
With regard to splicing fiber optical rods, it is known to coat the peripheral surface of the glass members to be joined with a thin adhering metallic layer. The coated glass members are properly positioned adjacent one another and solder is flowed around the joint between the members. While such a joint is strong enough to maintain the fiber optical rods in an aligned joint, there is no teaching that such a joint would or could be strong enough for joining structural members. In particular, the metallic layer is formed from a glass adhering paste designated "Bright Platinum, 0.5X, Paste". Such a metallic paste is very, very expensive, and therefore wholly unsuitable for a large scale application. The method of this invention, which provides a joint strong enough to join structural members, may be practiced with nearly any high temperature resistant adhesive and relatively inexpensive solderable metallic particles, such as copper.
In the area of decorative stained glass, a tinnable surface is provided by edging each piece of glass with a thin strip of metal foil, which is soldered into a continuous metal perimeter. Such a joint is significantly weaker than that formed by the method taught in this invention, and is much more costly and time consuming. Further, a metal foil joint must be caulked in order to weatherproof or waterproof the joint, whereas a joint made in accordance with this invention is inherently weatherproof and waterproof.
All of the disadvantages of the prior art methods for soldering to conventionally unsolderable surfaces are overcome by this invention, whereby any conventionally unsolderable surfaces may be joined by coating the surfaces with an adhesive, coating the adhesive with solderable metallic particles while the adhesive is tacky, and, after the adhesive is cured, soldering the surfaces together, the solder adhering to the metallic particles and forming a bond between the surfaces. The adhesive is preferably a high temperature resistant adhesive. The solderable metallic particles are preferably a combination of granules and powder, preferably copper. By the method of this invention, it is possible to solder to virtually any conventionally unsolderable surface, including glass, porcelain, wood, unsolderable metals such as steel and paper products. The method is also effective for joining a solderable surface or material to a conventionally unsolderable surface or material.